The semiconductor industry is continuously moving toward the fabrication of smaller and more complex microelectronic components with higher performance. Memory cells are an important component of many microelectronic components, and smaller memory cells that can store more information are desirable. The standard one bit memory cell can store one bit of data as either a logical “0” or a logical “1” state. A multi-level memory cell can store more than one bit of data. For example, a two bit memory cell can store 4 logical states of data (22) as either a “00”, a “01”, a “10”, or a “11”. A three bit memory cell can store eight bits of data (23), and so on. Multi-level memory cells frequently reduce manufacturing costs per bit of data stored, because the same production steps are used for multiple bits to achieve a higher density memory array for a given “footprint” or area. Multi-level memory cells also shrink the area required to store a bit of data, so smaller components are possible.
One type of memory cell is flash memory that is non-volatile and re-writable. Non-volatile memory retains stored information even when the memory cell is de-powered, and stored information can be changed when a memory cell is re-writable. Most multi-level memory cells in production today are non-volatile. Some memory cells for flash memory store information by either charging or draining an electrically isolated component, and the information is recalled by determining if the isolated component is charged or not. One type of memory cell used for flash memory is a thin film storage cell that uses discrete storage crystals, called silicon nanocrystals, to hold the charge. The storage crystals are relatively small, so thin film storage cells are useful for reducing the size of memory cells. However, the use of thin film storage cells for multi-level memory cells could decrease the area required to store a set amount of information.
Accordingly, it is desirable to provide multi-level memory cells with reduced size, and methods for producing the same. In addition, it is desirable to provide non-volatile flash multi-level memory cells using thin film storage layers, where the memory cell is re-writable. It is also desirable to provide methods for producing such memory cells. Furthermore, other desirable features and characteristics of the present embodiment will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.